Adult GEMMs harboring combinations of latent, inactive alleles of the four most common somatic lesions observed in human CRC (Cancer Genome Atlas Network, 2012) (APC, TP53, KRAS and BRAF) were subjected to surgically restricted delivery of AdCre to the distal colon; mice were then followed longitudinally for tumor progression via endoscopy, and tumor material was harvested as previously described (Hung et al., 2010; Martin et al., 2013). The gene discussed is BRAF; the disease is colorectal carcinoma.